1. Field of the Invention
The present invention relates to a supervisory control method and device for a network including a plurality of communication devices.
2. Description of the Related Art
In a network monitoring system in which the states of a plurality of communication devices are monitored by using a polling scheme, an inquiry is sent to each communication device and the state of each communication device is determined depending on whether or not a response is received. For example, referring to FIG. 1, a supervisory controller 1 sends a polling packet (health check packet) to each of communication devices 2 in predetermined order (S1). If the supervisory controller 1 receives a response packet to the polling packet from a communication device 2 within a predetermined period of time (S2), the supervisory controller 1 can confirm the soundness of the communication device 2, which is a target of monitoring. Hereinafter, the elapsed time from the transmission of an inquiry (polling packet) until the receipt of a response (response packet) will be referred to as “response time,” the predetermined time for which the supervisory controller 1 waits for a response will be referred to as “response wait time,” and the interval at which an inquiry (polling packet) is sent will be referred to as “polling interval” or “transmission interval.”
Various techniques have been proposed regarding polling-based supervisory control. For example, Japanese Patent Application Unexamined Publication No. H8-223191 discloses a health check system in which the response wait time is set for each device based on statistics on the response time of the device, whereby health checking is performed according to the processing load on each device.
Moreover, Japanese Patent Application Unexamined Publication No. H10-327148 discloses a communication network management method in which an increase in traffic caused by polling is avoided by varying the intervals (transmission intervals) at which a management device sends a diagnostic request, depending on the state of the network traffic.
However, in a case where a single supervisory controller monitors a large number of communication devices, the load on the supervisory controller is increased if the response wait time is set for each individual communication device, or if the polling intervals are dynamically varied with changes in the state of communication.